1. Field of the Invention
The present invention relates to navigation devices and, more specifically, to a navigation device structured as usable both inside and outside a vehicle.
2. Description of the Background Art
Conventional vehicle navigation devices display a map and a present position of a vehicle on the map, and search for an optimal route from a starting point to a destination point for guiding a driver. Such a vehicle navigation device is usually mounted fixedly inside the vehicle, and therefore the user cannot use the device outside the vehicle or inside another vehicle. To avoid such inconvenience, research and development has been carried out on navigation devices removable from the vehicle for portable use both inside and outside the vehicle. Such navigation device is exemplarily disclosed in Japanese Patent Laid-Open Publication No. 10-318763, which is described below with reference to FIGS. 24a and 24b. 
In FIG. 24a, a navigation device Nc is structured by a main device 101, a GPS (Global Positioning System) antenna 102, and an autonomous navigation sensor 103. The main device 103 is removably mounted on an arm stand 104 fixed in the vicinity of a driver""s seat of a vehicle for various operations required for navigating the user. When used inside the vehicle, the navigation device Nc is typically mounted on a dashboard. On the other hand, when used outside the vehicle, the antenna 102 is mounted on an antenna mounting portion 105. Provided on the antenna mounting portion 105 is a micro switch 106 that turns on when the antenna 102 is mounted.
When the above-structured navigation device Nc is used inside the vehicle, the main device 101 is fixedly mounted on the arm stand 104, and supplied with power by a battery provided in the vehicle through a power cable, cigarette socket or others. Moreover, the main device 101 makes a connection with the autonomous navigation sensor 103. Thus, the main device 101 carries out various operations required for user""s navigation, which are similar to the conventional ones.
When the navigation device Nc is used outside the vehicle, the user first removes the power cable and autonomous navigation sensor 103 from the main device 101. When the power cable is removed, the main device 101 is automatically supplied with electric power by an internal battery. The user also removes the antenna 102 from the dashboard, and then mounts it on the antenna mounting portion 105. The user then removes the main device 101 from the arm stand 104. Once the antenna 102 is mounted on the antenna mounting portion 105, the micro switch 106 is ON. The state of the micro switch is always monitored by a controller (not shown) of the main device 101. When the micro switch is ON, the controller determines that the main device has been out of the vehicle, and the operation mode is changed to portable mode as shown in a flow chart of FIG. 24b. 
In portable mode, the controller stores the present position and the present time when the main device 101 was out of the vehicle, as the present position of the vehicle and the time. The controller also stores cartographic data that has been used until the main device 101 was removed. The cartographic data represents a map covering an area adjacent to the present position of the vehicle (step S1001).
Next, the controller waits for a predetermined time (step S1002), and then detects the present position of the user based on a signal from a GPS satellite (step S1003). The controller further checks whether the detected present position of the user is within a predetermined range of distance (step S1004). If within the range, the procedure goes to step S1005. Otherwise, the procedure goes to step S1006.
In step S1005, the controller checks whether the micro switch is ON, that is, whether the antenna 102 has been removed from the antenna mounting portion 105. If the antenna 102 has been removed, the controller determines that the user came back inside the vehicle, and ends the portable mode. If the micro switch is ON in step S1005, the controller determines that the user is around the vehicle within the predetermined range of distance therefrom, and the procedure goes to step S1006.
In step S1006, the controller checks whether the present position of the user is at a predetermined distance (100 meters, for example) or more from the position previously stored. If the present position is within the predetermined distance, the procedure returns to step S1002 to repeat the process. If, on the other hand, the present position is at 100 meters or more away from the stored position, the controller chronologically stores a set of the present position and the present time (step S1007). Then, the procedure returns to step S1002 to repeat the process.
As described above, the navigation device Nc stores the position when the main device 101 was out of the vehicle as the position of the vehicle. Then, as the user travels the predetermined distance or more, the main device 101 stores the position of the user and the time of the movement. In other words, the controller stores a path of the traveling user. Then, in response to an operation by the user, the controller makes the map, with the path of travel overlaid thereon, displayed on a screen of the main device 101. Thus, the user can recognize his/her own path of travel, and come back to the vehicle along the path. Moreover, with an operation by the user, the controller searches for a route from the present position of the user to the vehicle position, and guides the user to the vehicle along the route.
In portable mode, the conventional navigation device Nc guides the vehicle and the user outside the vehicle. On the other hand, the conventional navigation device Nc guides the vehicle as such when the main device 101 is mounted on the arm stand 104. There is a big difference, however, between guiding users and guiding vehicles. For example, the user can only travel within an area much smaller than that the vehicle can. Therefore, the navigation device Nc can preferably display a relatively small area in detail in portable mode, while displaying a relatively large area when guiding the vehicle. However, even in portable mode, the navigation device Nc uses cartographic data used for guiding the vehicle and displays a map covering a larger area with the path of the traveling user overlaid thereon.
Furthermore, different traffic regulations are applied to pedestrians and vehicles. Therefore, the navigation device Nc searches for a route for guiding the user to the vehicle with the aid of the map used for guiding the vehicle, but the found route is not necessarily optimal for the user as a pedestrian.
As is evident from the above, the navigation device Nc carries out the same operation when used both inside and outside the vehicle, and therefore cannot provide guidance suitable for pedestrians.
Therefore, an object of the present invention is to provide a navigation device that can automatically determine whether it is used inside or outside a vehicle, and operate in an appropriate mode.
To achieve the object above, the present invention is directed to a navigation device that can be used inside and outside a vehicle, the device comprising a determination part for determining whether the device is used inside or outside the vehicle, and a navigation processing unit. When the determination unit determines that the device is used inside the vehicle, the navigation unit carries out first navigation suitable for use inside of the vehicle. When the determination unit determines that the device is used outside the vehicle, the navigation unit carries out second navigation suitable for use outside of the vehicle.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.